Catcapsules for self-healing applications

ABSTRACT

Materials and methods for preparing payload-containing microcapsules with walls that have orthogonal functionality are described. In some embodiments, the microcapsule comprises a material having a polymer matrix filled with a self-healing agent, and the microcapsule is modified with a catalyst and an orthogonally-bound silica support.

FIELD OF THE DISCLOSURE

Materials and methods described herein relate to self-healing materials.

BACKGROUND

Cracking in polymeric materials, such as thermosetting polymers, can behighly problematic as it leads to the degradation and failure ofdevices. These cracks occur not only on the surface of the devices, butcan also occur on the inside, which are not usually detected by visualinspection. Cracking can cause fiber-matrix interfacial debonding, plydelamination, and simple matrix delamination, which then can lead todegradation and more often than not, complete failure. These cracks canform from thermal and mechanical stresses during the use of thepolymeric material. In circuit boards, for example, these cracks canlead to electrical component failure.

In conventional self-healing applications that utilize microcapsules, acatalyst is either blended into the resin along with the microcapsules,or is encapsulated as well, and then blended with the resin-containingmicrocapsules into a polymeric resin. In these two examples, the crackmust be sufficient to expose both the catalyst and the resin (e.g.,cracking both a resin-containing capsule and a catalyst-containingcapsule). Additionally, in conventional applications, when the catalystis directly against the microcapsule, the chances of the self-healingagent being released becomes reduced because the catalyst reacts tooclose to the self-healing agent and essentially closes the capsule,thereby limiting flow into the cracks that have propagated through thepolymer.

SUMMARY

Embodiments described herein relate to materials and methods of makingmicrocapsules that have an encapsulated payload(s).

According to one embodiment, a method of making a microcapsule isprovided. The method includes forming a first microcapsule having apayload agent inside the microcapsule and an orthogonal-functionalizedunit incorporated into the wall of the microcapsule; and reacting thefirst microcapsule with a functionalized silica particle to form asecond microcapsule having an orthogonally-bound silica particle.

According to another embodiment, a microcapsule is provided. Themicrocapsule comprises a polymer matrix forming a wall of amicrocapsule; a payload agent inside the microcapsule; a catalyst; and asilica support, wherein the silica support is covalently linked to thepolymer matrix, and to the catalyst.

According to another embodiment, a method of making a microcapsule isprovided. The method includes forming a first microcapsule having afirst payload agent inside the microcapsule and a firstorthogonal-functionalized unit incorporated into the wall of the firstmicrocapsule; forming a second microcapsule having a second payloadagent inside the microcapsule and a second orthogonal-functionalizedunit incorporated into the wall of the second microcapsule; and reactingthe first microcapsule with the second microcapsule to form a linkedmicrocapsule.

Features and other benefits that characterize embodiments are set forthin the claims annexed hereto and forming a further part hereof. However,for a better understanding of the embodiments, and of the advantages andobjectives attained through their use, reference should be made to theDrawings and to the accompanying descriptive matter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, for the disclosure may admit to other equally effectiveembodiments.

FIG. 1 shows formation of an exemplary payload-filled microcapsuleaccording to some embodiments.

FIG. 2A is a flow chart illustrating the formation of an exemplarysilica support according to some embodiments.

FIG. 2B shows formation of exemplary modified silica particles accordingto some embodiments.

FIG. 3A shows an exemplary reaction between the modified silica particleand the orthogonal functionality of the microcapsule according to someembodiments.

FIG. 3B shows an exemplary reaction between an orthogonally-bound silicasupport of a microcapsule and a catalyst to form a CatCapsule, accordingto some embodiments.

FIG. 4 shows formation of a CatCapsule wherein the catalyst isseparately encapsulated from the self-healing agent according to someembodiments.

FIG. 5 is a general reaction scheme diagram illustrating the synthesisof a healing polymer produced during a healing event according to someembodiments.

DETAILED DESCRIPTION

The present disclosure relates to the formation of microcapsules havingencapsulated payloads. More particularly, some embodiments relate to aself-healing composite materials and microcapsules having encapsulatedself-healing agents.

Microcapsules are widely used as release systems containing, forexample, self-healing agents. The rupture and eventual release of thepayload is dependent on breaking the polymer shell, which is typicallydone mechanically through scratching, puncturing, or other mechanicalmeans directly applied to the polymer surface. The microcapsulesdescribed herein may be opened mechanically or chemically, as describedfurther below. As used herein, the term “microcapsule” is used to referto capsules that are in a range of about 10 microns to 1000 microns indiameter. However, it will be appreciated that the following disclosuremay be applied to capsules having a smaller size (also referred to as“nanocapsules”).

As used herein, the term “CatCapsule” is used to refer to microcapsulesand nanocapsules having a catalyst. CatCapsule can also be referred toas “Catpsule.” In some embodiments, the CatCapsules may be amicrocapsule comprising a material having a polymer matrix, wherein themicrocapsule is modified with a catalyst and an orthogonally-boundsilica support, and the microcapsule filled with a self-healing agent.Alternately, and in some embodiments, the CatCapsules may be amicrocapsule comprising i) a first microcapsule having orthogonalfunctionality encapsulating a catalyst and optionally a solvent;separately encapsulated from ii) a second microcapsule with orthogonalfunctionality encapsulating a self-healing agent and optionally asolvent. In some embodiments, the first microcapsule is covalentlybonded, optionally through a linking group, to the second microcapsule.

The disclosure herein relates to incorporating a self-healing agent intopolymeric microcapsules having an orthogonally-bound catalyst.Orthogonal means that the catalyst is bonded to the microcapsule using achemistry that does not respond to any materials in the microcapsule orthe environment of the microcapsule, such that if the microcapsule isruptured, the material inside is activated by the catalyst to reactwith, or within, the environment of the microcapsule without disruptingthe bond between the catalyst and the microcapsule. As discussed below,the orthogonal small molecule can bond to a catalyst species using achemistry orthogonal to the payload.

The orthogonally-bound catalyst allows for localization of the catalystcloser to the newly released resin that is being introduced due torupture of the microcapsule. For example, the catalyst is tethered tothe microcapsule, which allows for placement of the catalyst a setdistance away from the capsule shell, and prevents the self-healingagent closing only the capsule and not the crack throughout the polymermatrix. Moreover, the catalyst is able to react faster due to its closerproximity to the newly released resin. The distance may be empiricallydetermined. For example, the capsule diameter and the catalyst loadinglevel in the shell can be varied in a multivariate design of experimentsand the optimal conditions determined from the results.

CatCapsules, as disclosed herein, have the ability to autonomouslyself-heal cracks as a direct result of the incorporation of thenano/microcapsules into a polymer resin. The nano/microcapsules willrupture and supply a large amount of self-healing agent to a specificarea where a crack is forming. Due to the localization of the catalystbound on the surface of the microcapsule, the released self-healingagent can readily react with the catalyst and thus, allow for a fasterresponse when a capsule is ruptured.

The use of CatCapsules reduces the number of components to be added to apolymeric resin in order to generate self-healable materials. Bycreating an all-in-one microcapsule with orthogonally-bound catalyst,the processing steps are reduced due to fewer chemicals that need to beadded in order to generate self-healing composites. The steps to producethe self-healing composite are: dispersing the CatCapsules in solvent;blending the CatCapsule into a resin; and processing the composite. Anysuitable resin can be used including polyurethane, epoxies,polycarbonates, bio-based polymers, polyethylene terephthalate,fluoropolymers, polyvinyl chlorides, polyolefins, polysulfones,silicone, polyethylenimine, polyacrylates, polyimides, polyamides, otherpolyesters, and other polyethers. To use these resins, the healingchemistry should be compatible with the base polymer so that the resincan be healed. For example, if the base polymer is a polyurethane, theself-healing agent should comprise diol monomers and diisocyanatemonomers. One skilled in the art will know what self-healing agents (ormonomers) are needed to heal the various polymer resins.

Advantageously, these CatCapsules can be generated with homogenous sizedistributions allowing for controlled release; can be made to avoidreleasing payloads in undesirable situations; can be utilized as afunctional filler for polymer composites that will increase mechanicalstrength of the composite. The CatCapsules can find usage in multipleapplications including pharmaceutical products, insulation technologies,printed circuit boards, bezels, smart textiles, agricultural products,and consumer products such as food products, household products, andpersonal care products. For example, including the silica in theCatCapsules allows reduction or replacement of silica fillers that arepresent in many polymeric materials such as circuit boards.

This disclosure includes chemical structures that show atomiccompositions of compounds and relative bonding arrangements of atoms ina chemical compound. Unless specifically stated, the geometricarrangement of atoms shown in the chemical structures is not intended tobe an exact depiction of the geometric arrangement of every embodiment,and those skilled in the chemical arts will recognize that compounds maybe similar to, or the same as, the illustrated compounds while havingdifferent molecular shapes or conformations. For example, the structuresdenoted herein may show bonds extending in one direction, whileembodiments of the same compound may have the same bond extending in adifferent direction. Additionally, bond lengths and angles, Van derWaals interactions, isoelectronic structures, and the like may varyamong instances of the same chemical compound. Additionally, unlessotherwise noted, the disclosed structures cover all stereoisomers,conformers, rotamers, isomers, enantiomers, of the representedcompounds.

Numbered chemical structures are numbered using numbers, or numbers andletters, in parentheses. Numbered chemical reaction schemes are numberedusing numbers, or numbers and letters, in square brackets. Unlessotherwise noted, chemical reactions are performed at ambient conditionsor under slight heating with no special atmosphere or head space, andmay be performed using standard organic solvents to manage mixproperties such as viscosity and flow index.

According to some embodiments, and described below, the self-healingcomposite material is a CatCapsule. The CatCapsule may becatalyst-modified microcapsules with orthogonally-bound silica supports,wherein the microcapsule contains a self-healing agent. In an exemplaryprocess, and as described below a method of preparing CatCapsulesincludes preparation of self-healing microcapsules comprising orthogonalfunctionality; synthesis of a functionalized silica support; covalentlylinking the functionalized silica support with theorthogonal-functionalized microcapsule; and covalently linking acatalyst to the microcapsule having orthogonally-bound silica supports.These steps are set forth in their preferred order. It must beunderstood, however, that the various steps may occur simultaneously orat other times relative to one another. Moreover, those skilled in theart will appreciate that one or more steps may be omitted.

Prophetic Preparation of Microcapsules Comprising OrthogonalFunctionality

FIG. 1 shows formation of an exemplary payload-filled microcapsule,according to some embodiments. The payload is generally a liquid thatcan react to form a solid, and may be a self-healing agent. The shellsof the microcapsule are made of poly(urea-formaldehyde) groups and caninclude moieties or units that are orthogonally functionalized. In FIG.1, payload-filled microcapsules comprising orthogonal functionality 106are formed using an oil-in-water emulsion technique, also referred to asan emulsion polymerization, to create a protective polymeric shell 105around a payload core 101. The orthogonal functionality is incorporatedinto the polymeric shell 105, and is later used to attach a catalyst tothe polymeric shell 105.

In the example of FIG. 1, a payload 101 represents an oil phase that isdispersed into an aqueous continuous phase and stirred to begin anemulsion process. As illustrative, non-limiting examples, the payload101 (or multiple payloads) may include a self-healing agent, curingagents, a solvent, catalysts, or a combination thereof. One example of apayload agent 101 that may be used is a latent curing agent such asN-ethylpiperazine. It will be appreciated that various payload(s) may beselected to provide various functionalities for various applications.Other possible payloads 101 could be polymerizable molecules such ascyclic olefins, norbornene, substituted norbornene, cyclooctadiene,substituted cyclooctadiene, lactones, acrylates, acrylic acids,styrenes, isoprene, butadiene, molecules having isocyanate functionalgroups along with molecules having hydroxyl functional groups, andepoxies. In some cases, these agents may require an activator such as acatalyst and/or initiator. In some cases, these agents act asself-healing agents. Additionally, solvents could be incorporated intothe capsules which could be chosen from aprotic solvents, proticsolvents, or a mixture of the two.

A cross-linking agent 102, such as formaldehyde, is reacted with apolymeric emulsifying agent 103, such as ethylene maleic anhydridecopolymer, urea (or melamine), and orthogonal-functionalized smallmolecules 104 to form a capsule wall around the payload. Othercross-linking agents 102 may be used including glutaraldehyde, di-acidchloride, and derivatives thereof. The orthogonal-functionalized smallmolecules become a unit that is incorporated into the wall of themicrocapsule. Other polymeric emulsifying agents 103 may be usedincluding whey protein isolate, sodium caseinate, a surfactant, andderivatives thereof. These materials help to stabilize the emulsion sothat the capsule wall has time to form around the payload, but do notparticipate in formation of the capsule wall. Particle size may becontrolled by adjusting a stir speed during the reaction. For example, afaster stir speed may result in formation (on average) of smaller(“finer”) particles than a slower stir speed. Depending on whatsurfactant is used, the surfactant can also control particle size, suchthat more surfactant allows smaller particles to exist for a longerduration during the emulsion polymerization.

An example of orthogonal-functionalized small molecule 104 includesphloroglucinol (benzene-1,3,5-triol)-derivative 104A:

Structure 104A is an unsaturated mono-ether of the triol phloroglucinol.In structure 104A, R¹, R², R³ and R⁴ may be a hydrogen, alkyl group,alkenyl group, phenyl group, and alkoxy group.

The second part of the reaction diagram of FIG. 1, illustrates that acuring stage may be used to complete the reaction between thecross-linking agent and the polymeric emulsifying agent to form themicrocapsules or nanocapsules, the size of such capsules depending on astir speed. These microcapsules are then incorporated within a polymericmatrix 105 (also referred to as a polymeric shell) to which they wouldcovalently bind. The amount of microcapsules needed is empiricallydetermined based on the rheology of the resins, the particle size of themicrocapsule, and the amount needed to reach the desired payload contentfor release.

In another embodiment, the emulsion polymerization may contain a mixtureof different orthogonal-functionalized small molecules. Theorthogonal-functionalized small molecules may be mono-, di-, ortri-functionalized.

The payload-containing microcapsule with walls havingorthogonal-functionalized small molecules 104, or a combination oforthogonal-functionalized small molecules, may be prepared according tothe following process. To a stirring aqueous solution containing anethylene maleic anhydride (EMA) copolymer surfactant, urea (ormelamine), and ammonium chloride (NH₄Cl), an orthogonal-functionalizedsmall molecule (for example, 104A), or an orthogonal-functionalizedsmall molecule (for example, 104B), or a combination thereof, may beadded. The pH may be adjusted to about 3.5 by adding NaOH and HCl (orother suitable acids and bases), followed by the addition of anemulsifying agent (for example, a self-healing agent). The payload maybe added with other ingredients, such as monomers and/or pre-polymers,stabilizers, solvents, viscosity modifiers, odorants, colorant/dyes,blowing agents, antioxidants, or co-catalysts, or a combination thereof.Formaldehyde (or other suitable cross-linking agents) is added, whichacts as a curing agent to complete the polymeric shell formation. Theresulting microcapsules may be subsequently washed and sieved to removeunreacted material. Attachment of a catalyst that activates the payloadto solidify is described below.

Thus, FIG. 1 illustrates a particular embodiment of a process ofproducing a microcapsule (having an encapsulated payload). The capsulemay have orthogonal-functionalized small molecule 104, or a combinationof orthogonal-functionalized small molecules, as shown by microcapsule106. The payload, which may be a self-healing agent, is incorporatedinto a polymeric microcapsule that has small molecule blocks havingorthogonal functionality, affording the ability to covalently bind tothe polymeric matrix or to covalently bind to a separate moiety such asa silica support. After incorporation of the microcapsules into apolymeric matrix, an end user can rupture the capsules by various means,including using chemical means. An end user may also rupture and releasethe payload via scratching, puncturing, or other mechanical means.

As an example of another embodiment and as shown in Scheme 1, anorthogonal-functionalized small molecule 104 may be prepared accordingto the following process. To a stirring solution of phloroglucinol 107in THF and/or ether, at a temperature of about 0° C. to about roomtemperature, is added a sodium hydride (NaH) suspension, potassiumcarbonate (K₂CO₃), or triethylamine. Next, allyl chloride is added tothe stirring solution which is maintained at a temperature of about 0°C. to about room temperature, and then allowed to warm to roomtemperature to give 5-(allyloxy)benzene-1,3-diol (104A where R¹, R², R³,R⁴═H). For this reaction, any suitable base may be used, including ahydride base, a hydroxide base, or an amine base. Any suitable solventfor the reaction may be used, including ether and THF. A mixture ofmono-, di-, and tri-functionalized allyl ethers may form from thereaction. The amount of mono-, di- and tri-functionalized allyl etherscan be controlled by stoichiometry and dilute conditions. Mono-, di-,and tri-functionalized allyl ethers may participate in the emulsionpolymerization process.

The allyl-functionalized small molecule 104A is a non-limiting exampleof orthogonal-functionalized small molecules. The allyl group (or alkenegroup) is the orthogonal functionality in this case, and can be used toattach allyl-reactive species to the capsule. As described above, theallyl group is orthogonal because a payload and catalyst can be usedwhere they do not react with the catalyst attachment resulting from useof the allyl group. Other examples of orthogonal groups, as shown below,include alkyne structures such as 104B (via reaction of phloroglucinolwith propargyl chloride, for example), (meth)acrylate structures such as104D and 104E (via reaction of phloroglucinol with (meth)acryloylchloride, for example), and epoxy-functionalized phloroglucinol such as104C (via reaction of phloroglucinol with epichlorohydrin, for example)which can be used to react with the appropriate moiety within thepolymeric resin as well as the appropriate moiety of the modified silicaparticle. 104A-104E are monoethers of a triol.

wherein R¹, R², R³, R⁴, and R⁵ includes a hydrogen, alkyl group, alkenylgroup, phenyl group, and alkoxy group. The choice of R group can affectthe reaction between the orthogonal functionality of the microcapsuleand the functionalized silica support, as described below. Understandard conditions that react unsubstituted alkenes, alkynes, epoxies,and acrylates, the substituted version would likely show reducedreactivity. However, one skilled in the art would know of catalystsystems that allow for reaction of the substituted versions alkenes,alkynes, epoxies, and acrylates.

During formation of the orthogonal-functionalized small molecules104A-E, as described in Scheme 1, substitution at R¹, R², and R⁵ willlikely have minimal impact on the formation. For products 104A-C,substitution at R³ and R⁴ will lower reactivity during its formation,and therefore one skilled in the art would know to switch conditionsfrom S_(N)2 to S_(N)1 conditions. S_(N)1 conditions require polarsolvents like alcohols.

Any triol or functionalized triol, not just phloroglucinol, capable ofcapsule formation through emulsion polymerization can be used. Forexample, other functionalized triols may include functionalizedresveratrol (104F) and its isomers, functionalized alkyltriol (104G),functionalized naphthalenetriols (104H) and its isomers, functionalizedanthracenetriols (104J) and its isomers. Isomers include variedsubstitution of the hydroxyls on the phenyl rings and alkyl chains, aswell as cis and trans isomers. 104F, 104G, 104H, and 104J are monoethersof a triol

W includes allyl groups and substituted allyl groups, propargyl groupsand substituted propargyl groups, epoxy groups and substituted epoxygroups, acrylate groups and substituted acrylate groups, methacrylategroups and substituted methacrylate groups, and derivatives of each ofthese groups, as described above with phloroglucinol.

The orthogonal-functionalized small molecules 104 may be mono-, di-, andtri-functionalized. The amount of mono-, di- and tri-functionalizedorthogonal-functionalized small molecules can be controlled bystoichiometry and dilute conditions. Mono-, di-, and tri-functionalizedsmall molecules may participate in the emulsion polymerization process.

Microcapsules with orthogonal functionality at the surface thereofallows for the ability to bind (through, for example, the allyl group)into the polymer to increase rupture of the capsule, as describedthereof. For example, a chemically reactive functionality can be boundto the capsule that increases its susceptibility to rupture. Moreover,microcapsules with orthogonal functionality can provide for dualfunctionality. For example, microcapsules with orthogonal functionalitycan be used for filler materials having orthogonal flame retardants onthe outside of the capsule and a self-healing agent on the inside of thecapsule. For example, a phosphorus moiety can be incorporated into thecapsule wall, for example by including an orthogonal small molecule thatis a reaction product of phloroglucinol (or resveratrol, or any of theother triol materials described herein) with phosphoric acid, or anester thereof. Phosphate groups, phosphonate groups, and remaininghydroxyl groups, will react with urea, for example, in an emulsionpolymerization to attach the phosphorus moiety to the capsule wall. Inaddition, microcapsules with orthogonal functionality can covalentlybind to a silica support, as further described below, which may also actas a filler material.

Prophetic Preparation of Half-Functionalized Silica Supports

FIG. 2A shows a flow chart illustrating the formation of an exemplarysilica support according to some embodiments. The silica support may behalf-functionalized, as shown by 215 in FIG. 2B. These steps are setforth in their preferred order. It must be understood, however, that thevarious steps may occur simultaneously or at other times relative to oneanother. Moreover, those skilled in the art will appreciate that one ormore steps may be omitted.

Silica nanoparticles and microparticles may be prepared through amodified Stöber synthesis, at operation 201. Utilizing hydrolysis andcondensation of silica precursor tetraethoxysilane (TEOS) in ethanol,and in the presence of ammonia as catalyst (Stöber et al., ControlledGrowth of Monodisperse Silica Spheres in the Micron Size Range, J.Colloid Interface Sci. 1968, 26, 62-69), monodispersed silica particlesthat have diameters in the nanometer size range to micron size range maybe made. By varying the concentration of water in the synthesis, thediameter of the particles can be varied. After synthesis, the particlesmay be removed from their mother liquor solution to halt the growth ofthe particles and obtain the desired particle size.

As generally described above, silica particles (200 nm) may besynthesized by the following exemplary process. TEOS is distilled priorto use and all other chemicals were used as purchased. Ethanol (200proof, 5.38 mL) and TEOS (0.38 mL) are added to a 20 mL scintillationvial and shaken to mix. In a separate vial, 2M ammonia (3.75 mL) anddeionized water (0.49 mL) are added and shaken to mix. The ammoniasolution is then poured into the ethanol/TEOS solution and shaken for 10seconds. Vials were then left static for 24 h. After reaction period,particles are centrifuged and rinsed with ethanol at least 3 times toremove undesired particles and yielding silica nanoparticles. The finalmolar ratio of TEOS:ammonia:water was 1.00:4.39:15.95.

In preparation of a half-functionalized particle 215, an emulsion may beproduced, at operation 202 using a wax emulsion technique (e.g., usingparaffin wax). The emulsion contains cetyltrimethylammonium bromide(CTAB). CTAB facilitates silica particles gathering at the oil-waterinterface, thereby allowing reactants, compounds, components, and thelike to attach to the part of the silica that protrudes across theinterface into the oil phase.

The silica particles are dispersed in an ethanol/water solution (6.7%,w/w) and heated at an elevated temperature of about 65° C. (to melt thewax that will be added later). To the dispersion is added CTAB(commercially available from Sigma-Aldrich) (C_(CTAB)/S_(Silica)=5×10−6mol L-1m-2-S_(Silica)) with heating, to partially hydrophobize thesurface of the particles. A low concentration of CTAB is used to avoidthe creation of a bilayer at the surface of the particles. Paraffin wax(1.0 g, CAS no. 8002-74-2) is then added to the particle suspension.Once the wax has melted, the mixture is vigorously stirred (9000 rpm)for about 80 seconds at the elevated temperature to form an emulsion.The mixture is allowed to cool to about room temperature as the paraffinwax solidifies into solid droplets with the particles partiallyprotruding from the surface. The particles are washed with acid toremove the CTAB and expose a bare particle surface. The paraffin waxdroplets are then filtered. As illustrated by structure 210 in FIG. 2B,silica particles 211 partially extrude from a paraffin wax substrate212.

In a particular embodiment, the surface of the silica particles may thenbe modified with a coupling agent, such as a(3-mercaptopropyl)trimethoxysilane 213 solution in ethanol and aqueousammonia, at operation 203, to provide the modified silica particles inwax illustrated in structures 214A/214B. The coupling agent is used inorder to attach the particles to a resin, which may be a microcapsulehaving orthogonal functionality. Modification may be done with anysuitable coupling agent, so long as it is reactive towards themicrocapsule having orthogonal functionality. This silane modificationmay proceed according to the following exemplary process. The silicaparticles, as colloidosomes (e.g., the silica particles partiallyextruding from a paraffin wax) are dispersed into toluene (20 mL) andstirred to form a suspension. To the suspension is added(3-mercaptopropyl)trimethoxysilane (2.0 mL) in ethanol and aqueousammonia. The reaction is heated to about 45° C. and stirred for 48hours. The suspension is then cooled to room temperature to form soliddroplets of half-functionalized silica particles in paraffin wax 214A/B.As illustrated by FIG. 2B, structure 214A is a single silica particlewith surface thiol functionality, which partially protrudes from waxsubstrate 212; structure 214B shows multiple functionalized particlespartially extruding from wax.

At operation 204, the wax may be removed from modified silica particles214 to create half-functionalized silica particles 215 according to thefollowing exemplary process. The modified silica particles are removedfrom the wax by mixing the modified silica particles with a suitablesolvent at elevated temperatures. Suitable solvents include hydrocarbonsolvents such as benzene. The colloidal solution is separated byhigh-speed centrifuge, and decanted at least three times and dried invacuo to provide half-functionalized particles free of wax shown atstructures 215A/215B.

These half-functionalized silica particles free of wax 215 are alsoreferred to as modified silica particles. In an embodiment, the modifiedsilica particles may be used to prepare microcapsules havingorthogonally-bound silica supports, as described below.

Prophetic Preparation of Microcapsules Having an Orthogonally-BoundCatalyst

FIGS. 3A and 3B show formation of a CatCapsule, according to someembodiments. The CatCapsules may be a microcapsule that incorporates aself-healing agent payload, and optionally a solvent, into the polymericmicrocapsule, as described above, wherein the polymeric microcapsule hasan orthogonally-bound catalyst. The orthogonally bound catalyst may begrafted onto an orthogonally-bound silica support of a microcapsule.

According to an embodiment, and referring to FIG. 3A, the thiol-modifiedsilica particles 301, which are free of wax, may undergo reaction with amicrocapsule having orthogonal functionality (for example, 106A, bearingan allyl group). The reaction produces a microcapsule withorthogonally-bound silica supports 303.

As shown in FIG. 3B, operation 302 may be a thiol-ene click reaction,which may be performed by the following exemplary process. To a solutionof microcapsule having orthogonal functionality 106 (for example, 106A)in a suitable solvent, such as chloroform, are added thiol-modifiedsilica particles 301, an amine base, and an initiator, such as2,2′-azobis(isobutyronitrile) (AIBN). The reaction may be heated totemperatures of about 60° C. to about 80° C. and stirred untilcompletion to provide a microcapsule with orthogonally-bound silicasupports 303. Other suitable solvents for the reaction include polaraprotic solvents such as tetrahydrofuran (THF), dimethyl sulfoxide(DMSO), acetonitrile, and dimethylformamide (DMF) as well as non-polaraprotic solvents such as toluene. Neat solvents or a mixture of solventsmay be used. Suitable amine bases for the reaction include triethylamineand N, N-diisopropylethylamine (DIPEA).

The thiol-ene click reaction may proceed using ultraviolet (UV) light(wavelength about 365 nm to about 405 nm) or heat. Suitablephotoinitiators include (2,4,6-trimethylbenzoyl)diphenylphosphine oxide(TMDPO), 2,2-dimethoxy-2-phenyl acetophenone (DMPA), benzophenone,thioxanthone, and camphorquinone. Photoinduced reactions can be run attemperatures of about room temperature. Suitable thermal initiatorsinclude AIBN and benzopinacol at 60° C. to about 80° C. Standardprocedures for solvent removal can be used. If a vacuum is used toremove the solvent, the pressure should be monitored to avoid rupturingthe microcapsule. Heat may also be added to dry the material, but theheat should remain at a temperature lower than the boiling points and/ormelting points of the microcapsule components.

It should be understood that other orthogonal-functionalizedmicrocapsules 106 may be used in to covalently link the microcapsule tothe silica support. These other orthogonal-functionalized microcapsulesmay be based off of orthogonal-functionalized small molecules 104, asdescribed above. For example, the propargyl group of 104B, which isincorporated in the wall of the microcapsule 106, can undergo athiol-yne click reaction with 301 to yield a product similar to 303,while the epoxy functionality of 104C can undergo a thiol-epoxy clickreaction, to give a product similar to 303.

For the thiol-yne click reaction, which will provide an alkenyl sulfide,the reagents are similar to the thiol-ene reaction. Suitable thermalinitiators such as AIBN may be used. Suitable photoinitiators may beused including TMDPO, DMPA, benzophenone, thioxanthone, andcamphorquinone. Other catalysts for the reaction include triethylborane,indium(III) bromide), cationic rhodium and iridium complexes, thoriumand uranium complexes, and caesium carbonate. Suitable solvents includethose used for the thiol-ene reaction. Standard procedures for solventremoval can be used. If a vacuum is used to remove the solvent, thepressure should be monitored to avoid rupturing the microcapsule. Heatmay also be added to dry the material, but the heat should remain at atemperature lower than the boiling points and/or melting points of themicrocapsule components.

For the thiol-epoxy click reaction, which produces a thiol-alcohol,various bases can be used. However, care must be taken to avoid unwantedside reactions and rupture of the microcapsule. Harsh bases such ashydroxyls and hydrides should likely be avoided. Carbonates and aminebases, particularly hindered or tertiary amines being less reactive, aresuitable. Moreover, mild reagents such as titanium (IV) isopropoxide cancatalyze the reaction. Those skilled in the art would be able to selectsuitable photochemical and thermochemical initiators for the reaction.Standard procedures for solvent removal can be used. If a vacuum is usedto remove the solvent, the pressure should be monitored to avoidrupturing the microcapsule. Heat may also be added to dry the material,but the heat should remain at a temperature lower than the boilingpoints and/or melting points of the microcapsule components.

Additionally, the thiol of 301 may undergo other thiol click reactions,or Michael additions, with other functional groups, such asmethacrylates 104D, and acrylates 104E, to form a microcapsule with anorthogonally bound silica support similar to 303. However, care must betaken to avid side reactions and rupture of the microcapsule. Harshbases such as hydroxyls and hydrides should likely be avoided.Carbonates and amine bases, particularly hindered or tertiary aminesbeing less reactive, are suitable. Moreover, mild reagents such astitanium (IV) isopropoxide can catalyze the reaction. Those skilled inthe art would be able to select suitable photochemical andthermochemical initiators for the reaction. Standard procedures forsolvent removal can be used. If a vacuum is used to remove the solvent,the pressure should be monitored to avoid rupturing the microcapsule.Heat may also be added to dry the material, but the heat should remainat a temperature lower than the boiling points and/or melting points ofthe microcapsule components.

In another embodiment, the walls of the microcapsules 106 containmixtures of two or more different orthogonal-functionalized smallmolecules 104. For example, the walls of the microcapsule may contain amixture of allylic and propargylic functionality, or a mixture of epoxyand propargylic functionality, which could then react with the thiols ofthe silica support. Such microcapsules, bearing multiple functionality,may allow for further synthetic manipulations towards divergent sets ofmicrocapsules.

FIG. 3B shows formation of a CatCapsule, according to some embodiments.The CatCapsules may be a microcapsule that incorporates a self-healingagent payload, and optionally a solvent, into the polymericmicrocapsule, as described above, wherein the polymeric microcapsule hasan orthogonally-bound catalyst. The orthogonally-bound catalyst may begrafted onto an orthogonally-bound silica support of a microcapsule toprovide a catalyst-modified microcapsule with orthogonally-bound silicasupport.

In an embodiment, a self-healing composite material may comprise aCatCapsule; and further comprise a base polymer including polylacticacid, polyurethane, epoxies, polycarbonates, bio-based polymers,polyethylene terephthalate, fluoropolymers, polyvinyl chlorides,polyolefins, polysulfones, silicone, polyethylenimine, polyacrylates,polyimides, polyamides, other polyesters, and other polyethers. To usethese resins, the healing chemistry should be compatible with the basepolymer so that the resin can be healed. For example, if the basepolymer is a polyurethane, the self-healing agent should comprise diolmonomers and diisocyanate monomers. One skilled in the art will knowwhat self-healing agents (or monomers) are needed to heal the variouspolymer resins.

According to an embodiment and referring to FIG. 3B, the grafting atoperation 311, may be performed according to the following exemplaryprocess. Inside a dry box, catalyst 310A is weighed into a vial anddissolved in any suitable solvent such as benzene. In a separate vialcontaining a stir bar, microcapsule with orthogonally-bound silicasupport 303 is weighed. The benzene solution of catalyst 310A is thentransferred to the vial containing the microcapsules. The mixture isthen capped and allowed to stir at about room temperature for about 46hours. The mixture is then filtered using a fritted disc extractionthimble to remove the benzene and the thimble containing the CatCapsuleis placed into a soxhlet extraction apparatus and capped with a septa.The apparatus is then removed from the dry box and placed under argon.Dichloromethane (DCM), or another suitable solvent, is added and thesolid is continuously extracted with a suitable solvent such as DCM for24 hours. The solid is then dried in vacuo for 24 hours to yieldCatCapsule 312. Standard procedures for solvent removal can be used. Ifa vacuum is used to remove the solvent, the pressure should be monitoredto avoid rupturing the microcapsule. Heat may also be added to dry thematerial, but the heat should remain at a temperature lower than theboiling points and/or melting points of the microcapsule components.

Catalyst 310A,[RuCl₂(1-(2,6-dimethyl-4-(3-(triethoxysilyl)propyl)phenyl)-3-mesityl-4,5-dihydroimidazol-2-ylidene)(═CH-o-iPrO-Ph)]may be prepared by the method described in D. Allen et al., Well-DefinedSilica-Supported Olefin Metathesis Catalysts, Organic Letters 2009, 26,62-69.

Other catalysts that can be covalently attached to the silica supportinclude 310B[RuCl₂(1,3-dimesityl-4-(3-triethoxysilyl)propyl)-dihydroimidazol-2-ylidene)(═CH-o-iPrO-Ph)]) which may be prepared by the method described in Allenet al.; 310C[RuCl₂((1,3-dimesityl-dihydroimidazol-2-ylidene)(═CH-o-iPrO-Ph-4-OCH₂—C(═C)—N═N—N(propyltrimethoxysilyl))]which may be prepared according to J. Lim et al., MesoporousSilica-Supported Catalysts for Metathesis: Application to a CirculatingFlow Reactor, Chemical Communications 2010, 46, 806-808, and referencescited therein; 310D[RuCl₂(1,3-dimesityl-4-(3-triethoxysilyl)propylcarbamate)-dihydroimidazol-2-ylidene)(═CH-o-iPrO-Ph)] which may be prepared by the method described in A.Monge-Marcet et al., Catalytic Applications of Recyclable SilicaImmobilized NHC-Ruthenium Complexes, Tetrahedron 2013, 69, 1, 341-348;310E [{(RO)3SiO}Mo(═NAr)(=CHtBu)(CH₂tBu)] (Ar=2,6-iPr₂C₆H₃) which may beprepared according to F. Blanc et al., Surface Versus Molecular SiloxyLigands in Well-Defined Olefin Metathesis Catalysts: [{(RO)3SiO}Mo(═NAr)(=CHtBu)(CH2tBu)], Angewandte Chemie International Edition2006, 45, 1216-1220; 310F [[{(RO)3SiO}Mo(═NAr)(=CHtBu)(NPh₂)](Ar=2,6-iPr₂C₆H₃)] which may be prepared according to F. Blanc et al.,Highly Active, Stable, and Selective Well-Defined Silica Supported MoImido Olefin Metathesis Catalysts, Journal of the American ChemicalSociety 2007, 129, 1044-1045; 310G [[{(RO)3SiO}Mo(═NAr)(=CHtBu)(OtBu)](Ar=2,6-iPr₂C₆H₃)] which may be prepared according to F. Blanc et. al.,Dramatic Enhancement of the Alkene Metathesis Activity of Mo ImidoAlkylidene Complexes Ipon Replacement of One tBuO By a Surface SiloxyLigand, Dalton Transactions 2008, 3156-3158; and tungsten imidoalkylidene catalyst (not shown) [(SiO)W(NAr)(CHtBu)(CH₂tBu)] which maybe prepared according to B. Rhers et al., A Well-Defined,Silica-Supported Tungsten Imido Alkylidene Olefin Metathesis Catalyst,Organometallics 2006, 25, 3554-3557. Of note, Schrock-type catalysts areless stable to air and moisture. It should be understood that thecatalysts described herein are only exemplary catalysts. Othercatalysts, particularly Ruthenium catalysts, may be used so long as thecatalyst is compatible with grafting onto a silica support.

These Ruthenium-based Grubbs-type catalysts are useful for olefinmetathesis to create polymers via ring-opening metathesis polymerizationor cross-metathesis. A ring-opening metathesis polymerization (ROMP) ofalkenes is a type of olefin metathesis chain growth polymerizationtypically catalyzed by ruthenium-based carbene complexes, such as Grubbscatalysts, particularly Grubbs second-generation catalysts. Otherorganometallic catalysts of transition metals such as tungsten,molybdenum (Schrock-type, i.e., 310C-310E), rhenium, and titaniumcarbene complexes are useful for ROMP and cross-metathesis. ROMP occursfor ring-opening metathesis polymerization monomers including strainedcyclic olefins, including norbornene, substituted norbornene,cyclooctadiene, substituted cyclooctadiene, derivatives of suchcompounds, and combinations thereof. Such cyclic olefins, andcombinations of different cyclic olefins may be encapsulated in themicrocapsule as a component of the self-healing agent(s).Cross-metathesis may occur for any suitable monomer including acyclicdienes and unsaturated esters, such as ethyl oleate (Ethyl(Z)-octadec-9-enoate), derivatives of unsaturated esters (such asunsaturated carbamates and amides). Such acyclic dienes, unsaturatedesters, and derivatives, and combinations thereof may be encapsulated inthe microcapsule as a component of the self-healing agent(s).

Another form of olefin metathesis that can be used with the presentdisclosure is acyclic diene metathesis (ADMET). ADMET is a type ofolefin metathesis that can be used to polymerize terminal acyclicdienes, and has high functional group tolerance. ADMET can be performedusing a wide range of catalysts, including Grubbs second-generationcatalysts and other catalysts as described in T. Haque et al., AcyclicDiene Metathesis (ADMET) Polymerization for Precise Synthesis ofDefect-Free Conjugated Polymers with Well-Defined Chain Ends, Catalysts2015, 5, 500-517. Acyclic dienes, and combinations of different acyclicdienes, may be encapsulated in the microcapsule as a component of theself-healing agent(s). Moreover, acrylate metathesis, a form ofcross-metathesis, of the self-healing agent (monomers) can be used toheal the polymer. Grubbs second-generation catalysts (including 310A and310B) are useful for acrylate metathesis. Acrylate metathesis can beperformed on monomers such as olefins, alpha, beta-unsaturated estersand their derivatives, and combinations thereof, using Grubbssecond-generation catalysts (including 310A and 310B). Such olefins,alpha, beta-unsaturated esters, and derivatives thereof (such as alpha,beta-unsaturated carbamates and amides), and combinations thereof may beused as part of the payload of the microcapsules

More than one type of monomer may be used as part of the payload of themicrocapsules.

It should be understood that any catalyst compatible with bonding tosilica can be used for the CatCapsules described herein.

Monomers, including those listed above and throughout the description,are chosen so as to be compatible with the base polymer so that theresin can be healed. One skilled in the art will know to use a standardselection of the common monomers for the base polymers. For example, ifthe base polymer is a polyurethane, the self-healing agent shouldcomprise diol monomers and diisocyanate monomers.

Suitable solvents inside the microcapsules and CatCapsules includesolvents that dissolve the self-healing agent monomers. Suitablesolvents include toluene, benzene, dichloromethane, acetone, chlorinatedbenzenes, dichloroethane, diethyl ether, and tetrahydrofuran. Neatsolvents or a mixture of solvents may be used.

The overall catalyst concentration of the CatCapsules can be very low inaccordance with the embodiments disclosed herein, as the catalysts onlyexist on the orthogonally-bound silica supports instead of existing asfree particles.

Thus, a method of making a microcapsule, or CatCapsule, as describedherein, comprises forming a first microcapsule having a payload agentinside the microcapsule and an orthogonal-functionalized small molecule(or unit) incorporated into the wall of the microcapsule, and optionallya solvent; and reacting the first microcapsule with a functionalizedsilica particle to form a second microcapsule having anorthogonally-bound silica particle. The method further comprisescovalently linking the second microcapsule with a catalyst. The payloadagent can be any monomer, or combinations of different monomers,described herein. The orthogonal-functionalized small molecule can beany orthogonal-functionalized small molecule described herein.

A microcapsule, or CatCapsule, as described herein, comprises a polymermatrix, a payload agent, a catalyst, and a silica support. The polymermatrix is formed from an orthogonal-functionalized small molecule, or acombination of orthogonal-functionalized small molecules, across-linking agent, NH₄Cl, a copolymer, and a solvent. The polymermatrix is covalently linked to the silica support, and the silicasupport is covalently linked to the catalyst. The catalyst comprises anymetathesis catalyst described herein. The payload agent can be amonomer, or combinations of different monomers, described herein. Theorthogonal-functionalized small molecule can be anyorthogonal-functionalized small molecule described herein.

Advantageously, by creating an all-in-one microcapsule withorthogonally-bound catalyst and a self-healing agent, the processingsteps are reduced due to fewer chemicals that need to be added in orderto generate self-healing composites. The steps to produce theself-healing composite are: dispersing the CatCapsules in solvent;blending the CatCapsule into a resin; and processing the composite. Anysuitable resin can be used including polyurethane, epoxies,polycarbonates, bio-based polymers, polyethylene terephthalate,fluoropolymers, polyvinyl chlorides, polyolefins, polysulfones,silicone, polyethylenimine, polyacrylates, polyimides, polyamides, otherpolyesters, and other polyethers. To use these resins, the healingchemistry should be compatible with the base polymer so that the resincan be healed. For example, if the base polymer is a polyurethane, theself-healing agent should comprise diol monomers and diisocyanatemonomers. One skilled in the art will know what self-healing agents (ormonomers) are needed to heal the various polymer resins; and processingthe composite.

Prophetic Preparation of a Material with Distinct Microcapsules

According to another embodiment, and referring to FIG. 4A, theCatCapsule may be a linked microcacapsule comprising i) a firstmicrocapsule having orthogonal functionality encapsulating a catalystand optionally a solvent; separately encapsulated from ii) a secondmicrocapsule with orthogonal functionality encapsulating a self-healingagent and optionally a solvent. In this embodiment, the firstmicrocapsule is covalently bonded, optionally through a linking group,to the second microcapsule. The orthogonal functionality of thecatalyst-encapsulated microcapsule may then bond with the self-healingagent microcapsule's orthogonal functionality or with the aid of acoupling agent. Here, the catalyst is close to the capsule, yetseparated by a distance.

For these embodiments, no silica support is needed. Coupling agents usedto bond the distinct microcapsules include isocyanate chains to reactwith residual poly(ureaformaldehyde) groups of the microcapsule. If anorthogonal functionality of the individual microcapsules is used to bondthe microcapsules together, those skilled in the art would be able todetermine appropriate reagents for such reaction. An example isillustrated below.

In an embodiment, a self-healing composite material may comprise aCatCapsule; and a base polymer including polylactic acid, polyurethane,epoxies, polycarbonates, bio-based polymers, polyethylene terephthalate,fluoropolymers, polyvinyl chlorides, polyolefins, polysulfones,silicone, polyethylenimine, polyacrylates, polyimides, polyamides, otherpolyesters, and other polyethers. To use these resins, the healingchemistry should be compatible with the base polymer so that the resincan be healed. For example, if the base polymer is a polyurethane, theself-healing agent should comprise diol monomers and diisocyanatemonomers. One skilled in the art will know what self-healing agents (ormonomers) are needed to heal the various polymer resins.

FIG. 4 shows formation of a CatCapsule wherein the catalyst isseparately encapsulated from the self-healing agent according to someembodiments. As shown in FIG. 4, the individual microcapsules 401 and402 can be bonded together by a polymerization (403) or a coupling(403′). The polymerization can be done by using ADMET chemistry asdescribed in T. Haque et al., Catalysts, 2015, 5, 500-517, to form 404.The reaction may create polymers or oligomers, rather than dimers. Haqueet al. show various Ruthenium-carbene complex catalysts such as[RuCl₂(CHPh)(PCy₃)₂], [RuCl₂(CHPh)(IMesH₂)(PCy₃)](IMesH₂=1,3-bis(2,4,6-trimethylphenyl)-2-imidazolidinylidene),[RuCl₂(CH-2-OiPr-C₆H₄)(IMesH₂)], and RuCl₂(CHPh)(IMesH₂)(3-BrC₅H₄N)₂].404 may be prepared according to the following exemplary process.Capsules 401 and 402 (concentration of capsules is about 90 μmol/mL toabout 270 μmol/mL) were added to toluene or dichloromethane (about 1.0mL to about 3.0 mL). A Ruthenium carbene catalyst (about 20 equiv. toabout 80 equiv.) is then added to the mixture, and the mixture is heatedto about 50° C. for up to 8 hours. Standard procedures for solventremoval can be used. If a vacuum is used to remove the solvent, thepressure should be monitored to avoid rupturing the microcapsule. Heatmay also be added to dry the material, but the heat should remain at atemperature lower than the boiling points and/or melting points of themicrocapsule components.

If a coupling is used to bond microcapsules 401 and 402, the followingexemplary process may be performed to make 404′. If an orthogonalfunctionality of the individual microcapsules is used to bond themicrocapsules together, those skilled in the art would be able todetermine appropriate reagents for such reaction. For example, alkenesmay be linked together using hydrosilanes or dithiols. If dithiols areused, thiol-ene chemistry, as described above, can be used. Standardprocedures for solvent removal can be used. If a vacuum is used toremove the solvent, the pressure should be monitored to avoid rupturingthe microcapsule. Heat may also be added to dry the material, but theheat should remain at a temperature lower than the boiling points and/ormelting points of the microcapsule components.

The orthogonal functionality of the microcapsules does not have to beused to couple the microcapsules together. Instead isocyanate chains toreact with residual poly(ureaformaldehyde) groups of the microcapsulecan be used.

Thus, a method of making microcapsules, or CatCapsules comprises forminga first microcapsule having a first payload agent inside themicrocapsule and a first orthogonal-functionalized unit incorporatedinto the wall of the first microcapsule; forming a second microcapsulehaving a second payload agent inside the microcapsule and a secondorthogonal-functionalized unit incorporated into the wall of the secondmicrocapsule; and reacting the first microcapsule with the secondmicrocapsule to form a linked microcapsule. The payload agent of thefirst microcapsule comprises a catalyst, a solvent, or a combinationthereof, and wherein the payload agent of the second microcapsulecomprises a monomer, a solvent, or a combination thereof. The monomermay any monomer, or combinations of different monomers, as describedherein. The catalyst may be any metathesis catalyst described herein.

The individual microcapsules may be synthesized according to proceduresdescribed herein. For example, the emulsion polymerization can beperformed, wherein the payload for one microcapsule is a self-healingagent and optionally a solvent, and the payload for another microcapsuleis a catalyst and optionally a solvent.

Suitable solvents for the microcapsules and CatCapsules include solventsthat dissolve the self-healing agent monomers and the catalysts.Suitable solvents include toluene, benzene, dichloromethane, acetone,chlorinated benzenes, dichloroethane, diethyl ether, andtetrahydrofuran. Neat solvents or a mixture of solvents may be used.

Prophetic Preparation of a Self-Healing Composite Material

Referring to FIG. 5, which is a general reaction scheme diagram thatillustrates the synthesis of a self-healing polymer during a healingevent in accordance with some embodiments. A crack, for example, maydevelop in or on the surface of the self-healing composite material 501.The crack (e.g., about 1-2 microns wide) may rupture nearby CatCapsuleswhen the propagating crack comes in contact with the microcapsules. Whenthis occurs, the self-healing agent(s) 502, which are optionallydissolved in a solvent, flows from the CatCapsules and fills in thecrack due to capillary action. As the self-healing agent(s) flows fromthe CatCapsules, the agent comes into contact with the catalyst that istethered a certain length away from the CatCapsules. Contact between theself-healing agent(s) and the catalyst facilitates homogeneouspolymerization. The healing polymer 503 is the product of thishomogeneous polymerization. The synthesis of the healing polymer in thecrack may seal the crack.

In an embodiment, the CatCapsule of the self-healing composite material501 referred to in FIG. 5, which may comprise a catalyst-modifiedmicrocapsule with orthogonally-bound silica support, and wherein themicrocapsule contains self-healing agents and optionally a solvent.Alternately, in an embodiment, the CatCapsule may be a self-healingcomposite material 501 comprising i) a first microcapsule havingorthogonal functionality encapsulating a catalyst and optionally asolvent; separately encapsulated from ii) a second microcapsule withorthogonal functionality encapsulating self-healing agents andoptionally a solvent. In this embodiment, the first microcapsule iscovalently bonded, optionally through a linking group, to the secondmicrocapsule. The self-healing agents may be any agent described herein.The catalyst may be any metathesis catalyst described herein.

In an embodiment, the self-healing composite material comprises aCatCapsule, and a base polymer including polylactic acid, polyurethane,epoxies, polycarbonates, bio-based polymers, polyethylene terephthalate,fluoropolymers, polyvinyl chlorides, polyolefins, polysulfones,silicone, polyethylenimine, polyacrylates, polyimides, polyamides, otherpolyesters, and other polyethers. To use these resins, the healingchemistry should be compatible with the base polymer so that the resincan be healed. For example, if the base polymer is a polyurethane, theself-healing agent should comprise diol monomers and diisocyanatemonomers. One skilled in the art will know what self-healing agents (ormonomers) are needed to heal the various polymer resins.

According to another embodiment, a method for synthesizing a healingpolymer in a self-healing composite material comprising a base polymer(as described herein), comprises a CatCapsule dispersed in a basepolymer and optionally a solvent, and rupturing the CatCapsules. Themethod may further comprise rupturing the CatCapsules to release theself-healing agent monomers and bring the released monomers in contactwith a catalyst, and wherein the released self-healing agent monomer ispolymerized. The CatCapsules may be made according to any embodimentherein. Self-healing agents may be any agent described herein. Thecatalyst may be any metathesis catalyst described herein.

The descriptions of the various embodiments of the present disclosurehave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

1-13. (canceled)
 14. A method of making a linked microcapsule,comprising: forming a first microcapsule having a first payload agentinside the first microcapsule and a first orthogonal-functionalized unitincorporated into a wall of the first microcapsule; forming a secondmicrocapsule having a second payload agent inside the secondmicrocapsule and a second orthogonal-functionalized unit incorporatedinto a wall of the second microcapsule; and forming a linkedmicrocapsule by reacting: (a) the first microcapsule with the secondmicrocapsule in an acyclic diene metathesis reaction, (b) the firstmicrocapsule with the second microcapsule in a thiol-ene click reaction,(c) the first microcapsule with the second microcapsule in a thiol-yneclick reaction, (d) the first microcapsule with the second microcapsulein a thiol-epoxy click reaction, (e) the first microcapsule with thesecond microcapsule in a Michael reaction, or (f) a mixture of anisocyanate, the first microcapsule, and the second microcapsule.
 15. Themethod of claim 14, wherein the first payload agent comprises acatalyst, a solvent, or a combination thereof, and wherein the secondpayload agent comprises a monomer, a solvent, or a combination thereof.16. The method of claim 15, wherein the monomer comprises a ring-openingmetathesis monomer, a cross-metathesis monomer, an acyclic dienemetathesis (ADMET) monomer, an acrylate metathesis monomer, orcombinations thereof.
 17. The method of claim 16, wherein thering-opening metathesis monomer comprises a cyclic olefin, wherein thecross-metathesis monomer comprises an acyclic diene, an unsaturatedester, derivatives of the unsaturated ester, or combinations thereof,wherein the ADMET monomer comprises an acyclic diene, and wherein theacrylate metathesis monomer comprises alpha, beta-unsaturated esters,derivatives thereof, or combinations thereof.
 18. The method of claim15, wherein the catalyst comprises a ring-opening metathesispolymerization catalyst, a cross-metathesis catalyst, an ADMET catalyst,or an acrylate metathesis catalyst.
 19. The method of claim 15, whereinthe wall of the first microcapsule or the second microcapsule is formedfrom a reaction mixture comprising: one or moreorthogonal-functionalized small molecules, a cross-linking agent, NH₄Cl,a copolymer, and a solvent.
 20. The method of claim 19, wherein theorthogonal-functionalized small molecule comprises a monoether of atriol.
 21. The method of claim 19, wherein the cross-linking agent isselected from the group consisting of formaldehyde, glutaraldehyde,di-acid chloride, and derivatives thereof.
 22. The method of claim 19,wherein the copolymer is selected from the group consisting of ethylenemaleic anhydride, whey protein isolate, sodium caseinate, a surfactant,and derivatives thereof.
 23. A method of making a linked microcapsule,comprising: forming a first microcapsule having a first payload agentinside the first microcapsule and a first orthogonal-functionalized unitincorporated into a wall of the first microcapsule; forming a secondmicrocapsule having a second payload agent inside the secondmicrocapsule and a second orthogonal-functionalized unit incorporatedinto a wall of the second microcapsule, wherein the wall of the firstmicrocapsule or the second microcapsule is formed from a reactionmixture comprising: one or more orthogonal-functionalized smallmolecules, a cross-linking agent, NH₄Cl, a copolymer, and a solvent; andforming a linked microcapsule by reacting: (a) the first microcapsulewith the second microcapsule in an acyclic diene metathesis reaction,(b) the first microcapsule with the second microcapsule in a thiol-eneclick reaction, (c) the first microcapsule with the second microcapsulein a thiol-yne click reaction, (d) the first microcapsule with thesecond microcapsule in a thiol-epoxy click reaction, (e) the firstmicrocapsule with the second microcapsule in a Michael reaction, or (f)a mixture of an isocyanate, the first microcapsule, and the secondmicrocapsule.
 24. The method of claim 23, wherein the first payloadagent comprises a catalyst, a solvent, or a combination thereof, andwherein the second payload agent comprises a monomer, a solvent, or acombination thereof.
 25. The method of claim 24, wherein the monomercomprises a ring-opening metathesis monomer, a cross-metathesis monomer,an acyclic diene metathesis monomer, an acrylate metathesis (ADMET)monomer, or combinations thereof.
 26. The method of claim 25, whereinthe ring-opening metathesis monomer comprises a cyclic olefin, whereinthe cross-metathesis monomer comprises an acyclic diene, an unsaturatedester, derivatives of the unsaturated ester, or combinations thereof,wherein the ADMET monomer comprises an acyclic diene, and wherein theacrylate metathesis monomer comprises alpha, beta-unsaturated esters,derivatives thereof, or combinations thereof.
 27. The method of claim24, wherein the catalyst comprises a ring-opening metathesispolymerization catalyst, a cross-metathesis catalyst, an ADMET catalyst,or an acrylate metathesis catalyst.
 28. The method of claim 19, whereinthe orthogonal-functionalized small molecule comprises a monoether of atriol.
 29. The method of claim 23, wherein the cross-linking agent isselected from the group consisting of formaldehyde, glutaraldehyde,di-acid chloride, and derivatives thereof.
 30. The method of claim 23,wherein the copolymer is selected from the group consisting of ethylenemaleic anhydride, whey protein isolate, sodium caseinate, a surfactant,and derivatives thereof.
 31. A method of making a linked microcapsule,comprising: forming a first microcapsule having a catalyst, a solvent,or a combination thereof, inside the first microcapsule, and a firstorthogonal-functionalized unit incorporated into a wall of the firstmicrocapsule; forming a second microcapsule having a monomer, a solvent,or a combination thereof, inside the second microcapsule, and a secondorthogonal-functionalized unit incorporated into a wall of the secondmicrocapsule; and forming a linked microcapsule by reacting: (a) thefirst microcapsule with the second microcapsule in an acyclic dienemetathesis reaction, (b) the first microcapsule with the secondmicrocapsule in a thiol-ene click reaction, (c) the first microcapsulewith the second microcapsule in a thiol-yne click reaction, (d) thefirst microcapsule with the second microcapsule in a thiol-epoxy clickreaction, (e) the first microcapsule with the second microcapsule in aMichael reaction, or (f) a mixture of an isocyanate, the firstmicrocapsule, and the second microcapsule.
 32. The method of claim 31,wherein the monomer comprises a cyclic olefin, an acyclic diene, anunsaturated ester, derivatives of the unsaturated ester, an acyclicdiene, alpha, beta-unsaturated ester, derivatives alpha,beta-unsaturated ester, or combinations thereof, and the catalystcomprises a ring-opening metathesis polymerization catalyst, across-metathesis catalyst, an acyclic diene metathesis (ADMET) catalyst,or an acrylate metathesis catalyst.
 33. The method of claim 31, whereinthe orthogonal-functionalized small molecule comprises a monoether of atriol.